Web of Trust

Web of Trust

Overview

Unlike a government issued identity, in a global society, people can identify each other with cryptography.

In a Web of Trust system, peers validate the identity of other peers. This forms a network of reputation. This system is modeled after real life trust systems, such as the 5-star rating for restaurants.

Core concepts we'll be showing is how to use GnuPG to share your digital identity, digitally sign the identities of others, and receive signatures from others.

Sharing your Keys

After generating your keys from either the Simple or Advanced steps, you will want to publish your keys so others can find them.

Currently, there are 4 popular ways of sharing keys.

  • OpenPGP Key servers (SKS and Hagrid)
  • DNS Records
    • PKA Records
    • PGP Cert Records
    • IPGP Cert Records
  • Keybase
  • WKD - Web Key Directory

Most common way to share keys is publishing to key servers.

Key servers will eventually share data between each other, so generally if you publish to one server, the rest will receive at some point. These servers are old and not well maintained, so it may be best practice to publish to multiple servers anyhow.

  1. Obtain your pgp key fingerprint
gpg --list-keys youremail@domain.com

Note: your fingerprint will be a 40 character string

  1. Share your key with a key server
  • keyserver.ubuntu.com
  • pgp.mit.edu
  • keys.gnupg.net
  • keys2.kfwebs.net
gpg \
  --keyserver keys.gnupg.net \
  --send-keys ABCDEF0123456789ABCDEF0123456789ABCEDF01

Importing Signatures

There are different conventions for sharing signatures. Some people that sign your key may opt to publish the signatures to key servers on your behalf. If someone has chosen to do this, then you are all set and don't need to do anything. That said, there are very good reasons as to why that is bad practice, unless you know someone very well and have your permission.

When dealing with a stranger, or just to use best practices, you want to prove they own the email address linked to their keychain as well as proving they actually control the key they said is theirs.

A common method of doing this is signing someone's individual email addresses in their keys (called UIDs), encrypting the signature data to the claimed keychain, then emailing those signature “packets” to each email address listed. These steps prove they own the email address and can decrypt data sent to that key. These practices avoid you being tricked into signing a key owned by someone else.

If someone has emailed you encrypted signatures, you can decrypt, import, and publish them as follows:

  1. Download any encrypted signatures from your email. Encrypted files will almost always ends in .asc, however, these steps will work regardless of how the file is named.

  2. Import key of individual who signed you

gpg --recv-keys ABCDEF0123456789ABCDEF0123456789ABCEDF01

  1. Decrypt and import signature file
gpg --decrypt encrypted.asc | gpg --import
  1. Verify new signature
gpg --list-sigs youremail@domain.com
  1. Publish new signature
gpg \
  --keyserver keyserver.ubuntu.com \
  --send-keys ABCDEF0123456789ABCDEF0123456789ABCEDF01

Creating Signatures

To sign another person's key you will need your Master Key which is the only one with the Certify permission on your keychain. The Certify permission allows you to certify a change to your key or a signature added to someone else's.

If you followed our Simple steps for setting up a GPG smartcard, then your certified key is on the card you use everyday.

If you followed the Advanced steps, your certified key is likely on another GPG smartcard than the one you use everyday.

  1. Import key to be signed
gpg --recv-keys ABCDEF0123456789ABCDEF0123456789ABCEDF01
  1. Sign key
gpg --ask-cert-level --sign-key ABCDEF0123456789ABCDEF0123456789ABCEDF01
  1. Encrypt signature
gpg --export theiremail@domain.com \
  | gpg \
    --sign \
    --encrypt \
    --armor \
    --recipient ABCDEF0123456789ABCDEF0123456789ABCEDF01 \
  > encryptedsig.asc
  1. Email encrypted file with signature to signee

References

https://gpg.wtf